Facile Insertion of Rh and Ir into a Boron–Phenyl Bond, Leading to Boryl/Bis(phosphine) PBP Pincer Complexes

Abstract

The unexpectedly facile insertion of Rh or Ir into a B-Ph bond (reversible for Rh) converts a borane/bis(phosphine) precursor into a boryl/bis(phosphine) PBP pincer ligand. Interconversions between the boryl/borane/borate central functionality are demonstrated in reactions with dihydrogen.

A Tale of Two Elements: The Lewis Acidity/Basicity Umpolung of Boron and Phosphorus

“…Thea nalogous fluorophosphonium compounds derived from ferrocenyl-phosphines [CpFe(h 5 (50)w ere prepared. [81] In ap arallel study,t he fluorophosphonium cations 51-53 derived from Ph 2 P(C 6 Cl 5 ), PhP(C 6 Cl 5 ) 2 ,a nd (C 6 F 5 )P-(C 6 Cl 5 ) 2 [80] as well as af amily of phenoxy-derived EPC salts [(RO)P(C 6 F 5 ) 3 ][B(C 6 F 5 ) 4 ](R= Ph 54,4-FC 6 H 4 55,2,4-F 2 C 6 H 3 56,C 6 F 5 57)w ere also prepared (Scheme 13).…”

“…[4] Boryl ligands can be generated by oxidative addition of B-H, B-B,and B-halide bonds to transition metals and such species have been applied in av ariety of borylation reactions. [5] Related boryl anion adducts of boranes have also been described by reaction of diboranes (Bpin) 2 with bases and have been used in transmetalation and boryl anion transfer reactions. [6] Herein, we focus our attention on the formation and reactivity of isolable boron-based nucleophiles…”

“…[34] Ther elated borylene (CAAC)(NHC)BCN (24)w as prepared by reaction of the tetramer [(CAAC)B(CN)] 4 with an NHC. [35] Similarly,species based on oxazol-2-ylidene ligands of formulations L 2 BH were prepared and reported by Kinjo et al [36] Theoxazol-2-ylidene derivative (Me 2 H 2 C 3 N(Me)O) 2 )BPh (25;S cheme 5) can be readily protonated with acid and coordinated to metals to give Cr(CO) 5 ,A uCl, and (NHC)Au + derivatives. [37] More recently, such borylenes have served as precursors to diborylene dications [38] and azaborabutadienes.…”

Elucidating the Reactivity of Vicinal Dicarbenoids: From Lewis Adduct Formation to B−C Bond Activation

“…[4] Another formal example is the insertion of iridium and rhodiumi nto ab oranebisphosphine ligand,y ieldingP BPtype pincercomplexes. [5] Much like their transition-metal congeners, singletc arbenes possess al one pair and an empty orbital in spatial and energetic proximity and are as such able to mimic the process of oxidative addition. In recent years, these substances have been utilized fort he activation of variouse lement-elementb onds as well as smallm olecules (Scheme 1), an area of research that was for decades confined to organometallic reagents.…”

“…Crystallographicallydetermined solid-state structure of 2 (one of three independent molecules is shown). Thermalellipsoids are set at 50 % probability.Hydrogen atoms have been omittedf or clarity.S elected bond lengths []a nd angles [8]: B1ÀC1 1.663(6),B2 ÀC2 1.659(6), C1ÀC2 1.516(4), B1ÀC3 1.605(6), B2ÀC4 1.612(6), C1ÀN1 1.286(5),C2 ÀN2 1.296 (5). temperature or with gentle heating, the compound undergoes as ubsequentr eaction, which can be observed by ac olor change to yellow.T he final product was characterized by mul-tinuclearN MR spectroscopy.T he 11 BNMR spectrum shows as lightly broadened resonancea t9ppm, suggesting ab onding interaction of the boron atom with one of the piperidyl nitrogen atoms.…”